All spell casters gain their abilities through a form of demon possession. So in order to gain magical abilites, PCs must track down and trap demons. Of course there are some pretty powerful demons, if the demon is stronger than the PC, the PC could find themselves subjugated to the Demon's will.
There are two major (read feuding) provinces in the kingdom. The Lord of one is secretly a mad, power-hungry despot, constantly plotting against the king. The Lady of the other is secretly an ancient silver dragon.